There are a lot of studies that prove diesel fumes ON school buses are dangerously high, especially to those who are on board for long periods.  I have driven a school bus.  I have been sick for weeks and last year it was the same.  A home health care provider delivered a nebulizer to my home recently and told me that I am the 6th school bus driver in our area he has delivered one to since January (an unusually high percentage).
I told my pulmonist today and he seemed upset (I thought he was upset at me, but he could have been upset about the fumes - I don't know)  He said I had to stop taking my advair and my singulair for two weeks and then schedule a methylcholine challenge.  I guess to prove that I DO have bronchial asthma, or to prove that I don't.  
I don't understand if I have it or don't, I still have a problem with the fumes and have made consistent statements of that to my bosses.  I am not a sue happy person.  I just want to be well.   I am afraid if I stay out of work long enough to get well they will fire me, or not renew my contract in may, so therefore I would be without health insurance through the summer (recouperating time).